My understanding is that the drivers are the same. The difference being the part that holds the ear cup is made of aluminum on the 1's, as opposed to plastic on the 2's. Also, the 1's come in a nice box. I maybe wrong and if so I stand corrected.
My listening indicates that the RS series is not only better but they also seem to be cut from a different cloth. Better highs, deeper bass and tighter bass. I hear as much differences between the HP's and RS as I do between HP's and other manufaturers.
Go with the RS. The real question is whether the price difference between the 1's and 2's are worth it to you.